People shred documents for different reasons. Ordinary documents may be shredded to make disposal easier rather than to make them difficult to read by prying eyes. Sensitive documents are more likely to be shredded for data security reasons and to prevent the theft of trade secrets, customer lists, personal identity, and other confidential information.
Whether it is safe to throw out shredded documents depends on the confidentiality level of the data they contain and the type of shredder you use. It is not safe to throw out highly sensitive material shredded by your standard home or office machine because it can easily be reassembled manually.
You should always dispose of documents containing confidential information with data security in mind, whether you are a business or a private individual. The security level of certain documents is higher than others, so you should make sure that such records are clearly identified and shredded with a medium to a high-security shredder where possible. The better the shredder, the safer it is to throw them out.
Different Types Of Shredders
The ordinary home and office shredder is usually a strip-cut machine that renders sheets of paper into strips. A determined data thief can quickly assemble these to reconstitute a document. Strip-cut shredders are less expensive and faster than other shredders, and for this reason, many businesses and private individuals buy them, but they do not offer much security. They shred the paper into a relatively small number of large fragments that can be manually pieced together again like a jigsaw puzzle.
One security step up from a strip shredder is a cross-cut shredder that cuts the paper crosswise and lengthwise. When you feed paper into this kind of shredder, the result is a bit like confetti. Although it is much more challenging to reconstruct paper that has been shredded in this manner, it can be done, depending on how small the fragments are. There are very sophisticated computer-based methods these days for reassembling shredded documents.
Any document classified as confidential or higher, such as secret, should be shredded by a cross-cut shredder, not a strip-cut shredder. The cross-cut shredder should be high-end and not entry-level.
A good cross-cut shredder can reduce a page to more than four hundred pieces compared to a strip-cut shredder fifty-three. It is 7.5 times more secure than a strip-cut machine. The greater the number of fragments and the smaller they are, the more security a shredder provides.
If the documents contain confidential and personal information that could lead to identity theft, you can probably safely throw them away if you have shredded them in a cross-cut shredder. However, you should split the pieces across several different bins so they are not all together in the same place. It is inadvisable to allow shredded documents to accumulate outside in garbage bags or unlocked containers for any length of time.
Particle shredders are usually too expensive for small businesses and households, but they may be available at your office if you work for a large enterprise with equally large security risks such as a government department or industrial corporation. There are now data protection laws in many countries that affect how you store and dispose of sensitive information.
This means that legal risks are attached to how sensitive documentation is disposed of even without the criminal element getting hold of them. The laws differ from country to country.
In the US, secure disposal is required when a record contains personally identifiable information such as social security numbers, email and physical addresses, phone numbers, and names. Any personal information unique to an individual that can be used to identify them must be securely disposed of. Some laws even mandate the shredding of certain documents before disposal.
Security Levels For Shredders
Shredders are classified into different security levels. Level 1 security is the average strip-cut shredder that cuts an A4 size piece of paper into around 40 pieces. This is not suitable for sensitive documents like bank statements. Level 2 is also a strip-cut shredder, but the number of fragments produced by an A4-sized page is around 100, so the strips are much thinner. You should not use this kind for sensitive documents either.
Level 3 is a typical cross-cut shredder and can be used for confidential documents. This is recommended for sensitive documents used by small businesses and private individuals, such as personnel records, sales and marketing plans, and bank statements. It is regarded as medium security. Some level 3 shredders are not cross-cutters but rip the paper into very fine strips less than 2mm wide.
Level 4 is medium to high security and can be used for secret documents. These kinds of papers contain information that could damage personal or institutional privacy and safety if they get into the wrong hands. Industrial espionage is a thing, and companies wanting to foil would-be spies need to use this kind of shredder for delicate documents. The law in some countries may require a more secure means of disposal than merely throwing these documents in the trash.
Level 4 shredders are also cross-cut shredders, but they have to be able to reduce the documents to particles of less than 2mm by 15mm. They are often called Micro-cut shredders.
Level 5 shredders are for top-secret documents and can shred to a particle size of 0.8 by 12mm. These are for military and government-level institutions dealing with state secrets and matters of national security.
Level 6 shredders are regarded as maximum security machines that produce particles less than 0.8 mm by 4 mm. These are the highest level of security and are usually only used by government and military offices.
Shredded Documents Can Be Reassembled
There are a few historical examples of shredded documents being reassembled, even if it is an arduous and time-consuming process.
In 2009 federal prosecutors told a court they had begun reassembling documents shredded by a financial group charged with running a seven billion dollar Ponzi scheme. Technicians fed the scraps of paper into a scanner that transferred them onto a computer. A software program then automatically reassembled the scraps into their original form.
Such software is available for purchase even to home users. All you need is a personal computer and a scanner. Before this, shredded documents had to be reassembled manually.
In 1979 militants who took over the American embassy in Tehran used carpet weavers to reconstruct shredded CIA documents that were later published in a series of some sixty volumes. It took the Iranians some years to assemble all the pieces, but they used the information to identify people who collaborated with the CIA.
In 2011 DARPA (Defense Advanced Research Projects Agency) issued a challenge to computer scientists to reconstruct five shredded documents for a fifty-thousand dollar prize. They had to develop software that could put the papers back together and provide answers to puzzles embedded in them.
The winning team that completed the task consisted of three computer programmers, and they finished two days ahead of schedule. Their algorithm looked at factors such as the shape of the tears, fold marks, and writing on the paper.
One of the programmers said that DARPA’s challenge was relatively simple compared to a situation where there is a full bin full of shredded papers. It was easier to reconstruct the DARPA documents because they were neat, single-sided and all the pieces were laid right-side-up. They were also clean of dirt. Nevertheless, this was some ten years ago, and technology has improved considerably in the intervening period.
Conclusions
Throwing shredded documents out in the trash does come with security risks. If the records are secret or top secret, it is never safe to throw them out in the trash even after being shredded. If they are confidential, and you have used a medium-security shredder, you can probably safely throw them out. If you have used a strip-cut shredder, it is not safe to throw them out, and you should find another means of secure disposal after shredding.
